LU-9489 lod: keep minimum LOVEA size

LU-9489 lod: keep minimum LOVEA size

For a PFL file, some of its component could be un-instantiated, and
their lov_ost_data_v1 array is not needed, we should keep its LOVEA
as small as possible.

An unstantiated component's stripe offset should be set.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: I1cd70399446f063dca4de5b61d7e1dc2c8dde37c
Reviewed-on: https://review.whamcloud.com/27089
Tested-by: Jenkins
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>